The presently popular graphic input device—the computer mouse—has many disadvantages, however no other device could replace it, despite various attempts and many patents in this field.
A pen-shaped device is highly desirable, to allow natural handwriting or drawing. For pointing at icons on a computer's screen, a pen may allow a user to precisely point at the desired location. A pen is easier to use.
The prior art mechanical mouse has lower reliability and requires more effort on the user's part, than a noncontact, ultrasonic device.
Various attempts at using ultrasonic waves in input devices have been made. There are two basic approaches: devices using waves propagating in a solid (writing pad) and devices using waves propagating in the air.
The latter type is considered preferable, since no continuous contact with the writing pad is required. Two basic implementations of this type are known in the art:
a. A pen-shaped device wherein both the ultrasonic transmitter and the receiver are located in the pen. Waves reflected off the writing surface have a Doppler shift indicative of the pen's movement. See for example:
Zuta Marc, U.S. Pat. No. 5,239,139—Ultrasonic digitizer pen having integrated transmitter and receiver.
b. A pointing device containing an ultrasonic transmitter, with the corresponding receiver being at a fixed location. Alternately, the transmitter is fixed and the receiver is installed in the pen. See for example:    1. U.S. Pat. No. 4,862,152—Milner Sonic positioning device    2. U.S. Pat. No. 4,682,159—Davison Apparatus and method for controlling a cursor on a computer display    3. U.S. Pat. No. 4,578,674—Baker, et al. Method and apparatus for wireless cursor position control    4. U.S. Pat. No. 5,315,512—Roth Apparatus and method for generating image representations of a body utilizing an ultrasonic imaging subsystem and a three-dimensional digitizer subsystem    5. U.S. Pat. No. 5,637,839—Yamaguchi, et al. Ultrasonic coordinate input apparatus    6. U.S. Pat. No. 6,151,014—Zloter, et al. Systems and processing algorithms for ultrasound time-of-flight digitizer systems    7. U.S. Pat. No. 4,953,141—Novak, et al. Sonic distance-measuring device    8. U.S. Pat. No. 4,777,329—Mallicoat Graphic input system    9. U.S. Pat. No. 4,814,552—Stefik, et al. Ultrasound position input device    10. U.S. Pat. No. 5,866,856—Holtzman Marking device for electronic presentation board    11. U.S. Pat. No. 5,308,936—Biggs, et al. Ultrasonic pen-type data input device    12. U.S. Pat. No. 5,434,370—Wilson, et al. Marking system with pen-up/pen-down tracking    13. U.S. Pat. No. 5,009,277—Sindeband, et al. Method and apparatus for position determination    14. U.S. Pat. No. 6,067,080—Holtzman Retrofittable apparatus for converting a substantially planar surface into an electronic data capture    15. U.S. Pat. No. 6,292,177—Holtzman, et al. Marking device for electronic presentation board    16. U.S. Pat. No. 6,326,565—Holtzman, et al. Marking device for electronic presentation board    17. U.S. Pat. No. 6,300,580—Shenholz, et al. Presentation board digitizer systems    18. U.S. Pat. No. 6,265,676—Zloter, et al. Systems and processing algorithms for ultrasound time-of-flight digitizer    19. U.S. Pat. No. 4,825,116—Itoh, et al. Transmitter-receiver of ultrasonic distance measuring device    20. U.S. Pat. No. 4,991,148—Gilchrist, Acoustic digitizing system    21. U.S. Pat. No. 5,280,457—Figueroa et al., Position detecting system    22. U.S. Pat. No. 5,517,579—Baron, et al., Handwriting input apparatus for handwriting recognition using more than one sensing technique    23. U.S. Pat. No. 6,373,003—Holtzman, Marking device for electronic presentation board    24. U.S. Pat. No. 6,392,330—Zloter et al., Cylindrical ultrasound receivers and transceivers formed from piezoelectric film.    25. WO 01/69281 A1—Serafini, Serge, et at., PDP PERSONAL DIGITAL PEN    26. DE 003036947 A Postl Wolfgang, SIEMENS AG, Coordinate measuring system    27. JP 2002-132436 A FUJITSU LTD
The cited prior art patents are included herein by reference.
Ultrasonic transducers for use in air usually operate at a relatively low frequency and have a narrow bandwidth, this limiting the available resolution of the system. Usually the measured time-of-flight (TOF) value is used for range computations, thus an error in time measurements results in an error in range. For example, an 1 mSec time measurement error translates into a 34 cm range error. See for example FIGS. 3A, 3B, 3C.
Signal processing may be used to somewhat enhance resolution, however this may require complex processing with its related higher cost, higher current consumption and slower response time of the graphic input device. Moreover, the device may be more sensitive to noise and the components' parameters. Anyway, there is a limit to the achievable resolution, when the starting point is a coarse measuring means.
It is known that the movement between a transmitter and a receiver generates a Doppler frequency and phase shift, which may be used for displacement evaluation. The displacement thus measured, however, gives no indication regarding the distance between transmitter and receiver—there is a range ambiguity. Moreover, only the value of the displacement is measured (a scalar) with no indication regarding the direction of that velocity. This may pose a problem if one desires to compute movement in useful X-Y coordinates. See for example FIGS. 1 and 2.
Height measurement is required if the device is to be used like a pen—the regular pen writes on paper when it is in contact with the paper, and ceases writing when its tip is raised above the paper. With an electronic pen, things are not so simple: prior art ultrasonic devices usually measure movement only in a horizontal plane.
Prior art solutions to the problem include, for example, sensing Up/down movements with a mechanical device, which is activated when the pen's tip comes into contact with the writing surface.
Such mechanical means may require an effort on the user's part for their activation, both a vertical activation force and an horizontal force due to friction between pen's tip and the writing surface.
Although just a tiny force may be required, one should consider the accumulating effect of these efforts, when the computer is used for prolonged time periods. Moreover, mechanical devices are prone to failure.
Furthermore, the above prior art means only gives an up/down binary indication.
It is highly desirable to measure the actual height of the pen above the writing surface. The changes in height, in real time, convey important information the user may desire to be processed in the computer. Prior art devices apparently do not provide means for fast height measurements, at a fine resolution.
Various input devices may require a special interface (hardware) and/or software, and may not be usable or compatible with existing software. This may limit the usefulness of these devices, especially for use at home or by people who are not computer experts.
An activation button, or a plurality thereof, may be desired, to provide a function akin that of the buttons in the PC mouse. When using a pen-shaped, high-resolution input device such as that in the present invention, pushing a mechanical button may create a noticeable disturbance in the precise pen's location or movement. The handwriting or drawing may include a mistake, or the wrong icon may be activated on screen.
Prior art high performance devices, such as digitizers, carry a high price and may be bulky.
It is an objective of the present invention to provide for a graphic input device with means for overcoming the abovedetailed, as well as other, deficiencies.